Derivatives and Other Financial Instruments - Schedule of Gains and Losses on Derivative Excluded from Assessment of Effectiveness Recognized in Current Earnings (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Amount of loss expected to be recognized into earnings over the next 12 months			$ 14
Earnings recognized in relation to ineffective portion of the hedging relationships	0	(5)	0	5
Amount of gain or (loss) recognized in earnings related amount excluded from the assessment of hedge effectiveness		2	(2)	1
Maximum [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain or (loss) recognized in earnings related amount excluded from the assessment of hedge effectiveness	$ 1